Soda Can Clock Using Arduino Pro Mini, DS3231 and Nokia 5110

This Instructable shows you an Arduino based clock that was integrated into a twin bell alarm clock made from soda cans.

The clock is using an Arduino pro mini, the DS3231 real time clock module, the Nokia 5110 LCD display and a 18650 Li-battery with a charger module. The code for the Arduino was explained here. However, some improvements were made concerning power consumption an therefore the code was updated and uploaded as supporting file in step 4. With a 2900 mAh battery the clock is running for 4 month.

The twin bell alarm clock from soda can was build like previously shown here. The project uses soda cans where the ink was removed.

Hope you like that project and please vote for me in the clocks contest.

Twin bell alarm clock:

• 1 big Soda Can with a diameter of 66 mm
• 2 smaller Soda Cans with a diameter of 53 mm
• 2 Screws with cap nuts, M4 x 20 mm (to fix the twin bells)
• 2 Screws with cap nuts, M4 x 30 mm (as legs for the main structure)

Arduino clock

• Arduino pro mini (3.3V, 8 MHz) 
• Nokia 5110 Display 
• RTC DS3231
• LIR2032 3.6V rechargeable button cell battery
• Micro USB 5V 1A 18650 Lithium Battery Charger Module
• Rechargeable 3.7V Li Battery 18650 PF 2900mah
• 18650 Battery Holder
• Cable for Breadboard
• Jumper Cable Wires Kit
• Breadboard with 55 holes
• Micro switch
• Single row male pin header strip
• Arduino download cable

Tools:

• Wire wrapping wire & tools
• Knife
• Piece of plywood with a thickness of 14 mm
• Scissor
• Pliers
• Can opener
• Computer
• Soldering station
• Electric drill
• Calipers

• The twin bells are made using the soda cans with a diameter of 53 mm.
• For easy separation of the bottom and the lid a jig from plywood with a thickness of 14 mm is used.
• Use a knife to make a score line around the can. Hold the knife on the jig at a level plane and then rotate the can around. It is not necessary to cut through the aluminum. Apply some pressure with an old credit card near the score line to separate the top and the bottom part (see video).
• Take the bottom part and make a strong groove on the inside.
• With pliers start to separate the aluminium to release the dome.
• Trim the dome with scissors so the dome forms a perfect circle.
• Place the dome on top of the lid and fix it with glue.
• Make a hole in the middle of the lid and enlarge it until you can push the screws through.

• Take the larger soda can.
• Cut the lid with a can opener (see video).
• Remove the lid with pliers.
• Use calipers to make a score line 67 mm from the top.
• Reduce the size of the soda can to the score line with scissors.
• Remove the ink from the soda cans. I already posted an Instructable how to remove the ink from soda cans. You can find it here (Link).
• Drill four holes in to the main structure. The holes for the legs are in a distance of 25 mm from the front an 55 mm apart from each other. Whereas the holes for the screws to mount the twin bells are in a distance of 35 mm from the front an 50 mm apart from each other.
• Attach the M4 x 20 mm screws to fix the twin bells
• Attach the M4 x 30 mm screws as legs for the main structure

In order that the clock fits into the soda can it has to be made in a compact way. Therefore the battery holder was chosen to act as a framework. The LCD display and the combination of Arduino-BreadBoard-RealTimeClock is fixed to the battery holder with adhesive tape.

In order to finish this project fast the wire wrapping technique (Link) was used to make to connection between the male header pins on LCD Display and the pins on the breadboard or Arduino. A small breadboard with only 55 holes was used.

The wiring was done according to the schematic drawing (see picture).

The battery charger module is glued with hot glue directly onto the battery holder.

The code how do convert the digital signal from the DS3231 into the analog clock was already explained in detail here. However, in this preliminary version, not much attention was paid to energy consumption. Therefore some improvements were necessary.

First of all an Arduino Pro Mini with 3.3V and 8MHz was chosen. Then the "powerlow" function was integrated in the code. In addition all the LEDs on the Arduino and the Real Time Clock Module were removed to result in the following:

• Code Version 07 12 mA without "powerlow" function
• Code Version 08 7 mA with "powerlow" function
• Arduino LED1 5 mA
• Arduino LED2 3 mA
• Real time module LED 1 mA

With 1mA per hour and a 2900mAh Lipo this clock will work for 4 month.

The time on the DS3231 was set using the following library:

https://github.com/jarzebski/Arduino-DS3231/blob/master/DS3231_intalarm/DS3231_intalarm.ino

After "Include Library" via "Add zip file" the code for the "DS3231_simple" is available under examples to set the time. Open the Arduino IDE. Connect the Arduino with your computer and remove the battery from the DS3231 clock module. Under "Tools" chose the right "Board" (Pro mini), the correct processor (ATmega 328T, 3.3V 8MHz) and the port. Then upload the «DS3231_Simple» and immediately open the serial monitor. Then the time from your computer will be use to set the time on the DS3231. Enter the battery again. Now as the time is adjusted upload the code for the analog clock.

Remove the edges from the Nokia LCD display so it will fit in the twin bell alarm clock. Enter the clock and fix it with tape to prevent it from sliding back.